1. Field of the Invention
The present invention relates to a method and an apparatus for generating a wobble clock signal, and more particularly, to a method and an apparatus capable of maintaining a stable rotation speed when the optical disc is processed.
2. Description of the Related Art
In general, a shallow groove is spirally etched on the optical disc outwards from the center of the optical disc such as the CD-R, CD-RW, DVD-R, DVD+RW, or DVD-RW when the optical disc is manufactured, and this groove is called as a “pregroove”. In fact, this pregroove is not a perfect spiral but with numerous wobbles. The “wobble” of the pregroove looks like a sinusoidal on the general press-made optical disc. Even this pregroove is so small and almost invisible, it can be detected by the optical driving unit in the optical drive apparatus, and the signal detected in the pregroove by the optical drive apparatus is a wobble signal whose frequency has been modulated. A certain time data is obtained after the wobble signal is demodulated by the optical drive apparatus, and this time data is referred as a “pregroove absolute time”, which is used to assure of maintaining the stable speed when the optical drive apparatus is processing the signal on the optical disc. Therefore, whether or not the pregroove is correct, and whether or not the pregroove is accurately read become major topics of the optical driving apparatus and the optical disc.
For example, when burning a recordable optical disc, if there is a defect on the recordable optical disc, the recordable optical disc apparatus cannot accurately determine the pregroove absolute time, thus an unstable and wrong pregroove absolute time is obtained. This causes that the rotation speed of the motor in the recordable optical disc apparatus become unstable, and degrades the CD burning quality.
In addition, the defect on the optical disc also deforms the wobble signal. A pregroove absolute time is extracted from the wobble signal on every predetermined cycle in the conventional technique. Therefore, when the wobble clock signal is deformed due to the defect on some area of the optical disc, the pregroove absolute time of the subsequent normal area is also impacted and becomes incorrect. Thus the CD burning quality is significantly impacted.